In the HVAC industry, flexible ducts are often used to connect a rigid sheet metal trunk (supply or return) duct to a terminal fitting, such as a boot (i.e., a transitional fitting with a round aperture at one end for connection to the flexible duct and a rectangular opening at the other end into which a register or grill may be fitted). Such a flexible duct generally comprises an inner sleeve of a Mylar® or similar polyester film containing a coil of wire to give it shape. (Mylar® is a registered trademark of the E.I. du Pont de Nemours and Company of Wilmington, Del.) This inner sleeve is then wrapped in fiberglass insulation, with an outer sleeve made of plastic or aluminum serving as an outermost layer for containing the insulation.
Currently, installation of such flexible ductwork first requires cutting a hole into the trunk duct, and then securing a fitting to the trunk duct using tabs and, optionally, a sealing adhesive gasket. The flexible duct is connected to the fitting by pulling the inner sleeve over the fitting, and then wrapping tape over the inner sleeve and fitting to secure and seal the flexible duct to the fitting. The insulation and outer sleeve are then pulled against the fitting with a zip tie. Of course, this is repeated at the terminal fitting. Such installation in the field is awkward and time consuming because the locations for connections are often cramped and difficult to reach, and the method requires wrapping the tape around the fittings while affixed in their permanent positions. Furthermore, the resultant connection is of variable quality and strength, and often leaks air. Accordingly, there remains a need in the art for an HVAC duct system that is easy to install and minimizes the likelihood of air leakage.